1. Field of the Invention
The present invention relates to an apparatus and method for translating a multiplexed packetized bus into a de-multiplexed bus which is easily accessible by external components. Furthermore, the present invention relates a structure and method for providing an internal and external boot for a self-contained processor system.
2. Art Background
A self-contained processor system includes components and features such as a processor, volatile memory, non-volatile memory, cache memory, timers, serial ports, etc. This system may exist on a single PCB (printed circuit board) or MCM (multi-chip module). Typically, a user or external device has very limited access to the internal components of the system. For example, the processor's non-volatile memory where start-up code is usually stored may be completely inaccessible to the external user.
To reduce the design cycle time and increase integration, MCM and PCB processor systems have become very widely used. The time and knowledge required to design with these types of systems is minimal, as the interface to the processor's bus had been previously designed and the external interface to the system bus typically is straight forward.
However, as the processor system is designed to be self-contained, internal bus operations and protocols are not designed with ease-of-use and external access requirements in mind. Therefor, access externally by a device coupled to operate with the self-contained system, or a user accessing the system for operational or debugging purposes is quite difficult.
A processor typically on boot-up will look for its configuration data at some predefined address in non-volatile memory. This address is fixed and cannot be changed by the user. The configuration data is generally stored in non-volatile memory off of the processor's local bus. In a self-contained processor system, this non-volatile memory is inaccessible to the external user.